I go pally aura when I am doing 4v4 rt tanks knights.
In 1v1 it depends, sometimes I max holy light, and then only do 1 divine shield, rest go to aura and ulti, and sometimes I don't and just go divine shield, if my enemy is something like Undead or is notorious for mass nuking and focusing heroes.
Devotion Aura is in fact better than even trueshot aura. +1.5 armor means about +8-9% damage reduction, meaning about 10% more effective HP. It then also affects not just ranged but melee and even worker units if you pally happens to be in your town.